This would help ensure countries in the region got their fair share of economic returns on tuna harvested from their waters, he said.

Tuna valued at more than US$3.3 billion ($3.9 billion) was harvested from Pacific waters last year, but only 14 per cent of that value - about US$460 million - made it back to Pacific nations.

Illegal, unreported and unregulated fishing needed to be monitored, McCully said at the Pacific Islands Forum in Palau today.

New Zealand was committed to the sustainable management of the region's fisheries.

"While Pacific countries are working successfully with regional agencies to boost their returns from fisheries, they have the right to expect a larger share of their greatest natural resource," he said.

Forum host nation Palau, located northwest of Papua New Guinea, manages nearly a third of the world's tuna stock through fishing quotas and conservation efforts, along with seven of its island neighbours.

Palau's President, Tommy Remengesau, has proposed completely closing the country's territorial waters, an area the size of France, to commercial fishing.

The marine sanctuary would create an area where tuna could breed and grow, ensuring stocks were healthy and gained in economic value, Remengesau said.

If Palau imposes the ban, it would be the first time a country had completely banned fishing vessels from its entire exclusive economic zone.

The major challenge faced by the tiny island nation, which has a population of just 21,000, was the ability to enforce the ban and stop illegal fishing in its waters using only a few patrol boats donated by Australia.

New technologies, including unmanned drones, have been trialled in Palau, and Remengesau is looking for other international partners to assist in enforcement and monitoring measures in the region.

New Zealand today signed the Niue Treaty Subsidiary Agreement on regional fisheries co-operation.

On top of $66m already committed over the next five years for fisheries management and development in the Pacific, McCully announced at the forum a further $4.6m to improve the management of fisheries information in the region.

"[The fisheries industry] is a very significant income stream for the region, it's the biggest economic asset that the region has got.

"Having information to ensure its proper use and management is really important and we are very pleased to be part of that process."

The importance of fisheries was a primary focus of New Zealand's Pacific Economic Development ambassador Shane Jones, McCully said.

"It's a careful line we walk, these are not our zones, these are Pacific countries' zones, but we play a big supportive role.

"Shane Jones' work in this area is very much welcomed by the Pacific leaders I've talked to, and I think it's going to be very important to the economic futures of Pacific countries in the years ahead."

The additional funding pledged would go to the regional Forum Fisheries Agency, which recognised sharing and analysing fisheries data was vital for monitoring and enforcement, McCully said.

"Our funding will implement national fisheries information management systems in all Forum Fisheries Agency countries, setting up e-reporting and e-monitoring of catch and stocks, and facilitating better co-ordination across the Pacific region."

New Zealand would showcase at the United Nations Small Islands Developing States conference in Apia, Samoa, in September how the region was using its collective strength to improve management and secure larger economic benefits from fisheries, McCully said.